Naked Pairs in Sudoku: The Intermediate Unlock
After Hidden Singles, the next leap for many solvers is the Naked Pair. It looks almost too simple: two cells in the same row, column, or box that contain exactly the same two candidates. Those two digits must live in those two cells — nowhere else in that house. Seeing the pair is the skill; trusting the elimination is the habit.
Two cells, two digits, zero room for anyone else.
What is a Naked Pair?
A Naked Pair is two cells in one house (row, column, or 3×3 box) whose candidate lists are identical and length two — for example both show only 3 and 8. Because those cells must be 3 and 8 in some order, every other cell in that house can drop 3 and 8 from its notes. The pair is "naked" because the candidates are fully visible in those two cells; you do not need to hunt for a hidden twin elsewhere.
How to find and use Naked Pairs
- Keep candidate notes current. Pairs hide in messy boards. After each placement, clear impossible digits so two-candidate cells stand out.
- Scan one house at a time. Pick a row, column, or box and look for two cells with the exact same two-digit set. Matching length is not enough — the digits must match.
- Lock the house, then eliminate. Those two digits are reserved. Erase them from every other cell in the same house, even if those cells look "almost filled."
- Watch for new singles and triples. A clean elimination often creates a Naked Single or reveals a Naked Triple. Chain the wins instead of jumping to a harder pattern too early.
Example: a {3,8} pair in row 5
Suppose r5c2 and r5c7 each contain exactly the candidates {3,8}. Because both cells share row 5 and the row must contain one 3 and one 8, those two digits are reserved for the pair—even though their order is still unknown.
- Verify the candidate sets. Both cells must contain exactly the same two candidates. A cell marked {3,8,9} cannot participate until 9 is removed by another valid rule.
- Limit the claim to the shared house. Erase 3 and 8 from every other unsolved cell in row 5. Do not automatically erase them from the entire columns or boxes unless both pair cells share that unit too.
- Rescan the affected cells. If another row-5 cell changes from {1,3} to {1}, place 1 and propagate its effects. The pair itself may remain unresolved for several moves.
Common Naked Pair mistakes
Using cells from different houses
Two matching cells form a useful pair only when they share a row, column, or 3×3 box. Matching notes in unrelated cells create no elimination.
Accepting unequal candidate sets
{3,8} and {3,8,9} are not a Naked Pair. Each participating cell must be restricted to exactly the same two digits.
Eliminating beyond the shared house
A row pair reserves digits within that row. Its cells may sit in different boxes, so the pair does not justify removing both digits from either whole box.
A Naked Pair practice checklist
- Update candidate notes before searching so false pairs do not survive from earlier moves.
- Scan one house at a time and group the cells that have exactly two candidates.
- After each elimination, look for a new naked single before searching for another pair.
Drill Naked Pairs on Medium and Hard Classic puzzles on Sudoku Hot. Once pairs feel automatic, Hidden Pairs and X-Wings become much easier to learn — they reuse the same "these digits are spoken for" mindset.
Naked Pairs FAQ
Does a Naked Pair tell me which digit goes in each cell?
No. It proves that the two cells contain the two digits in some order. Its immediate benefit is removing those digits from other cells in the shared house.
Can the same pair work in both a row and a box?
Yes. If both cells share a row and the same 3×3 box, you may eliminate the pair digits from other cells in both units.
What is the difference between a Naked Pair and a Hidden Pair?
A Naked Pair is visible because two cells contain only the same two candidates. A Hidden Pair occurs when two digits appear nowhere else in a house, even if their two cells initially contain extra notes.
